Abstract
A mutation is a change in the nucleotide sequence of an organism. Mutations are the primary means to new genetic variation within a population. Mutations are due to a wide variety of sources including viruses, errors in cell replication, and induction by mutagens. However, the question remains to be answered whether mutations are induced by the mutagen or are pre-existing within a population. We hypothesized that mutations for resistance to bacteriophage T2 were pre-existant within a population of E. coli. Based on our hypothesis, we predicted the observed number of resistant colonies should greatly increase upon re-spreading the micro-colonies after a short period of incubation. The experimental procedure involved plating E. coli onto to two different plates with T2 present on both plates. The plates were re-spread after a two hour incubation period. A titration of the culture was simultaneously conducted to determine the concentration of E. coli, which was used to determine the mutation frequency. Our results indicated that mutations are pre-existant within the population of E. coli, the number of resistant colonies was consistently greater on the re-spread plate. Chi-square analysis of the data showed a p value of .0001, which is extremely significant.